Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$132.72	8.678%	$144.2374	$144.24	$144.25	$144.20
Purchase #2	$119.58	6.400%	$127.2331	$127.23	$127.25	$127.20
Purchase #3	$182.31	9.636%	$199.8774	$199.88	$199.90	$199.90
Purchase #4	$56.25	12.572%	$63.3218	$63.32	$63.30	$63.30
Purchase #5	$220.48	12.779%	$248.6551	$248.66	$248.65	$248.70
Purchase #6	$62.26	12.171%	$69.8377	$69.84	$69.85	$69.80
Purchase #7	$141.83	11.778%	$158.5347	$158.53	$158.55	$158.50
7 purchase totals =	$915.43		$1,011.6972	$1,011.70	$1,011.75	$1,011.60